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#[cfg(no_std)]
use alloc::boxed::Box;
#[cfg(no_std)]
use once_cell::race::OnceBox;
#[cfg(std)]
use std::sync::LazyLock;
#[cfg(std)]
type Inner<T> = LazyLock<T, fn() -> T>;
#[cfg(no_std)]
type Inner<T> = OnceBox<T>;
/// Lazy static helper that uses [`LazyLock`] with `std` and [`OnceBox`] otherwise.
///
/// [`LazyLock`]: https://doc.rust-lang.org/stable/std/sync/struct.LazyLock.html
/// [`OnceBox`]: https://docs.rs/once_cell/latest/once_cell/race/struct.OnceBox.html
pub struct RacyLock<T: 'static> {
inner: Inner<T>,
#[cfg(no_std)]
init: fn() -> T,
}
impl<T: 'static> RacyLock<T> {
#[cfg(std)]
/// Creates a new [`RacyLock`], which will initialize using the provided `init` function.
pub const fn new(init: fn() -> T) -> Self {
Self {
inner: LazyLock::new(init),
}
}
#[cfg(no_std)]
/// Creates a new [`RacyLock`], which will initialize using the provided `init` function.
pub const fn new(init: fn() -> T) -> Self {
Self {
inner: OnceBox::new(),
init,
}
}
}
#[cfg(std)]
impl<T: 'static> core::ops::Deref for RacyLock<T> {
type Target = T;
/// Loads the internal value, initializing it if required.
fn deref(&self) -> &Self::Target {
&self.inner
}
}
#[cfg(no_std)]
impl<T: 'static> core::ops::Deref for RacyLock<T> {
type Target = T;
/// Loads the internal value, initializing it if required.
fn deref(&self) -> &Self::Target {
self.inner.get_or_init(|| Box::new((self.init)()))
}
}